46. Identification and characterization of genes crucial for basal freezing tolerance in an alpine subnival plant Chorispora bungeana

Abstract

Cold acclimation improves freezing tolerance in plants. Many advances have been made toward identifying the signaling and regulatory pathways that direct the low-temperature stress responses. However, little is known about the mechanisms for naturally freezing tolerant species such as Chorispora bungeana ( C. bungeana ). This novel plant grows in high attitude regions with temperature ranging from 4 °C to −10 °C. We aim to isolate genes that are crucial for basal tolerance in C. bungeana by suppression subtractive hybridization (SSH) with cold-treated (−4 °C) and non-cold treated plant samples combined with macroarray and real-time PCR analysis. A total of 85 genes including 52 up-regulated and 33 down-regulated genes were identified as candidates for basal freezing tolerance. These genes were sorted into broad functional categories including stress/hormone stimulus response, photosynthesis, transcription, protein metabolism, ribosomal protein, etc. This suggests that a very complex series of molecular mechanisms are involved in the response to freezing stress in C. bungeana . Functional analysis indicates that a fibrillin protein FBN1a and an ACTIN cross-linking protein may act as the cold sensors by their physical changes caused by cold, and DREB2A signal pathway combined with ABA signal pathway may play a critical role in regulating the COR genes (cold responsive genes). Meanwhile, the downstream cold responsive genes, such as KIN2 ( COR6.6 ), ZAT10 ( STZ ) and GR-RBP8 , also play a very important role in freezing tolerance. In addition to that, some new genes were also identified successfully which indicated that there may exist some new signal pathway or mechanisms in C. bungeana in response to freezing stress.